Conventionally, a maximum injection quantity and a minimum injection quantity is defined as indices indicating a performance of a fuel injection valve for injecting fuel into an internal combustion engine. The quantity of fuel that a fuel injection valve can inject by keeping valve-opening of the fuel injection valve for a prescribed period (for example, one second) is defined as the maximum injection quantity. Injecting a larger injection quantity in a unit time is desired for requirement of the maximum injection quantity, and it can be addressed by increasing, as a determination factor, a setting value of a part represented by a valve-body lift quantity (moving quantity) in the fuel injection valve or a nozzle diameter provided in a distal end of the fuel injection valve. Meanwhile, the minimum injection quantity indicates the smallest injection quantity with which the fuel injection valve can stably inject, and the injection quantity is desirably required to be smaller. By the way, the injection quantity with which injection can be stably performed can be inevitably reduced by shortening a valve-opening instruction time for the fuel injection valve. However, the injection quantity varies between injection valves with identical specifications and identical driving instruction time. Therefore, the variation in the injection quantity falling within a prescribed range is set as a requirement.
In recent years, technological development for widening the range (hereinafter referred to as a dynamic range) between the maximum injection quantity and the minimum injection quantity that has been already mentioned is actively made for an electromagnetic fuel injection valve of a direct-injection internal combustion engine in particular. Particularly, so-called half-lift control in which an active fuel injection is controlled from a state where the valve body of the fuel injection valve is not fully open is catching attention for further reducing the minimum injection quantity while keeping the conventional maximum injection quantity.
For example, in the technique of PTL 1, the half-lift control is realized by improving the mechanism of the fuel injection valve such that the lift quantity of the valve body can be fixed to two levels of a high lift and a low lift and by setting a driving current of the fuel injection valve for each level.
In the technique of PTL 2, half-lift control of an electromagnetic fuel injection valve is realized by performing control to supply a valve-opening current for opening the valve body against a fuel pressure upstream of the fuel injection valve for a short period of time to start closing the valve before reaching a state where the valve body is fully open such that the lift quantity of the valve body is in a parabolic motion.